B

Not since the first “Blair Witch” movie has a little horror indie created such buzz as “Paranormal Activity,” and Paramount Pictures obviously had visions of dollar signs in their corporate eyes when they picked up the movie for distribution after its successful premiere at the 2008 Slamdance Festival. After some expert trimming, fine-tuning and canny promotion through excitement-creating midnight screenings, the studio is releasing it to theatres, where it will undoubtedly rake in a hefty profit. After all, it was made for only $15,000, and even after you factor in editing and promotional costs (as well as those involved in post-production sprucing up of effects), it would be virtually impossible not to realize one.

The picture, written, directed, shot and edited by one-man band Oren Peli, isn’t much more than an extended exercise in horror tropes, but it’s a clever one, expertly designed and executed, depending more on pulse-pounding suggestion rather than explicit violence. Set in 2006, it follows a twentysomething San Diego couple (Micah Sloat and Katie Featherson) investigating poltergeisty phenomena that are bedeviling their house. Their basic technique is to set up a video camera to record what happens in their bedroom at night. (While they’re sleeping, you dirty-minded soul.)

The tapes reveal strange movements and shadows, and noises that wake them up. They call in a psychic (Mark Fredrichs) who tells them that the business might involve demons rather than ghosts and gives them the name of a demonologist to call, but Micah unwisely chooses to continue his own researches instead, even going against the expert’s advice by bringing in a Ouija board. His decision is particularly reckless because Katie’s admitted that she’s been troubled by these sorts of occurrences since she was a kid, which surely indicates that something’s following her around. And of course her boyfriend’s insistence on upping the ante only leads to an escalation of the devilish incursions.

This plot could easily have served as the basis for an hour-long Syfy Channel program, but “Paranormal Activity” is much better than that. Peli, Sloat, Featherson and Fredrichs take a naturalistic approach, occasioned perhaps by the meager resources but no less effective for that, which succeeds in getting the adrenaline going without resorting to crude splatter. The picture cannily ratchets up the tension step by step until it reaches a climax that’s played swiftly enough not to be ridiculous. And the gritty look—partially caused, one presumes, by blowing up the original to 35mm—is just right. Even the hand-held camerawork is the proper choice in this context. And the picture reminds us how much realistic sounds, as opposed to the cheap phony ones big-budget horrorshows regularly employ nowadays to accompany “gotcha” moments, can add to an unsettling atmosphere.

“Paranormal Activity” doesn’t reinvent the horror-movie wheel. It just uses the old-fashioned techniques well. It offers a salutary contrast to another recent Paramount picture, “Cloverfield,” which tried for a similar jolt but opted for a much bigger budget and far more extravagant devices to do so. The fact that it failed and this movie succeeds shows that the old story of the little engine that could (or is it the tortoise and the hare?) can still apply.